Chemistry Aldehydes & Ketones PMC 2021
PMDC Verified Question 45 of 94
Which of the following show positive iodoform test?
A
Butanol
B
Acetaldehyde
C
3-Pentanone
D
Formaldehyde
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Acetaldehyde
Concept:

The Iodoform test requires the presence of a methyl group adjacent to the carbonyl carbon (\( CH_3-CO- \)).

Solution:

  • Acetaldehyde has the structure \( CH_3-CHO \).


  • Because it contains the essential \( CH_3-CO- \) structural motif, it reacts with iodine and a base to form a yellow precipitate of Iodoform (\( CHI_3 \)).


  • Acetaldehyde is, in fact, the only aldehyde that gives a positive iodoform test.


Why other options are incorrect:

Butanol (1-butanol) lacks the \( CH_3-CH(OH)- \) group. 3-pentanone (diethyl ketone) has ethyl groups adjacent to the carbonyl, not methyl groups. Formaldehyde (\( HCHO \)) lacks a methyl group entirely.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

Previous Question All Aldehydes & Ketones MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App